Hitherto, there have been known the following processes for producing drawn filaments and drawn tapes having both high strength and high modulus from ultra-high-molecular-weight polyethylene.
(a) Japanese Patent Kokoku No. 60-47922
A heated solution of polyolefin in a concentration of 1 to 30% by weight is spun. PA1 (the present inventor's U.S. Pat. PA1 A single crystal aggregate mat obtained from a solution of polyethylene in a concentration of not more than 1% by weight is molded by extrusion at 70 to 135.degree. C. PA1 Communications", 26, 258 (1985)
(b) Japanese Patent Kokai No. 60-101032
No. 4,643,865)
An aggregate of gel particles obtained by cooling a polyethylene solution is compression molded at a temperature
lower than its dissolving temperature.
(c) Japanese Patent Kokai No. 58-217322
(d) Japanese Patent Kokoku No. 60-53690
A melt molded product from ultra-high-molecular-weight polyethylene is stretched at a temperature of higher than 150.degree. C.
(e) P. Smith, H. Chanzy and B. Rotzinger, "Polymer
A polyethylene film polymerized at a relatively low temperature is directly stretched without dissolving it.
However, in the above conventional processes of (a) and (b), a large amount of solvent is used and, in the process (c), a particularly large amount of solvent is used. Among these processes, although it is possible to produce filaments and the like having relatively large sectional area by the process (b), the process (a) is directed to production of fine filaments having the sectional area of less than 0.01 mm.sup.2 and, with increase in the sectional area of filaments, the resulting strength and modulus are decreased. The processes (d) and (e) are economical in that no solvent is used. However, both strength and modulus in the process (d) are much lower than those in the processes (a), (b) and (c). The process (e) is directed to stretching of small pieces which are polymerized in the form of thin films, and is not directed to a process for producing a long continuous drawn product having larger sectional area.